Large-diameter earth boring bit

ABSTRACT

A BIT FOR DRILLING LARGE-DIAMETER HOLES. CUTTERS ARE ARRANGED IN A STAGED CONFIGURATION AROUND A CENTRAL SHAFT. THE INNERMOST CUTTERS ARE THE SAME LARGE CUTTERS USED AT OTHER LOCATIONS ON THE BIT ALLOWING COMPLETE INTERCHANGEABILITY. THE INNERMOST CUTTERS ARE TURNED INWARD. THIS REDUCES THE INCUT BOTTOM NEXT TO THE PILOT HOLE AND PROVIDES A STRONGER BIT BECAUSE THE CENTRAL SHAFT HAS NOT BEEN WEAKENED BY MILLING OR OTHER OPERATIONS.

March 13, 1973 M. L. TALBERT LARGE-DIAMETER EARTH BORING BIT 3Shuts-Sheet 1 Original Filed March 9, 1970 FIG. 2

INVENTOR MILTON L. TALBERT l PRIOR ART PRIOR ART ATTORNEY March 13, 1973L TALBERT LARGE-DIAMETER EARTH BORING BIT 5 Sheets-Sheet 2 FIG. 3

ATTORNEY March 13., 1973 M. L. TALBER'f 27,597

LARGE-DIAMETER EARTH BORING BIT Original Filed March 9, 1970 3Sheets-Sheet 5 FIG. 4

INVENTOR v MILTON L. TALBERT ATTORNEY United States Patent Ofifice Re.27,597 Reissued Mar. 13, 1973 27,597 LARGE-DIAMETER EARTH BORING BITMilton L. Talbert, China Springs, Tex., amignor to Dresser Industries,Inc., Dallas, Tex.

Original No. 3,633,691, dated Jan. 1, 1972, Ser. No. 17,663, Mar. 9,1970. Application for reissue Apr. 4, 1972, Ser. No. 242,148

Int. Cl. E21b 9/24; E21c 23/00; EZld 3/00 US. Cl. 175-334 12 ClaimsMatter enclosed in heavy brackets appearsjn the original patent butforms no part of this reissue specification; matter printed in italicsindicates the additions made by reissue.

ABSTRACT OF THE DISCLOSURE A bit for drilling large-diameter holes.Cutters are arranged in a staged configuration around a central shaft.The innermost cutters are the same large cutters used at other locationson the bit allowing complete interchangeability. The innermost cuttersare turned inward. This reduces the uncut bottom next to the pilot holeand provides a stronger bit because the central shaft has not beenweakened by milling or other operations.

BACKGROUND OF THE INVENTION This invention relates to the art of earthboring and more particularly to an improved bit for drillinglargediameter holes. The bit of this invention is generally used in aboring operation wherein a relatively small pilot hole is first drilledand the hole enlarged by a subsequent reaming operation utilizing theimproved bit.

In bits of this character, it has been found desirable to employ anumber of small rolling or rotatable cutters rotatably mounted on a mainbit body. The cutters are located and spaced so that upon rotation ofthe hit every portion of the hole being drilled will be acted upon byone or more of the cutters to disintegrate the formation. This insuresthat almost the entire wear of drilling takes place on the cuttersrather than on the main bit body. The cutters should be readilyreplaceable thereby allowing the life of the bit to be extended byreplacing the cutters.

This type of bit is sometimes referred to as a raise bit because of itsextensive use in boring raise holes between levels of an undergroundmine. The term raise may have been applied to this type of operationbecause a pilot hole was drilled from one level of a mine down toanother level and the hole enlarged by a raising operation on the upwardpass. The bit of this invention may be used for boring raise holes andin other operations wherein a large-diameter hole is desired. This mayinclude boring at any angle to the horizontal either up or down and withor Without a pilot hole.

Many strict requirements are imposed upon a bit to be used in boringlarge-diameter holes. The bit must be a balanced high-performanceapparatus that is rugged and will perform for a long period of time. Itis desirable to have a majority of the elements wear out at about thesame time without premature failure of any one element. The bit isrepeatedly subjected to high stress and the particular geometry of thebit imposes limitations upon the structural elements that are exposed tothe stress.

DESCRIPTION OF THE PRIOR ART The prior art is in general represented byU.S. Pat. No. 3,220,494 to R. E. Cannon et al., patented Nov. 30, 1965.The system shown by the Cannon et a1. patent includes a rotary drillingapparatus for rotating and hydraulically raising a raise cutter headalong a pilot hole to form a raise hole between a lower level and anupper level of a mine.

The raise cutter head enlarges the pilot by reaming with its pluralityof staged cutters.

Large-diameter bits of the prior art have used d-iiferent sized cutters.The inner cutters were generally smaller than the other cutters becausethey had to be located as close to the central shaft as possible and thesmaller the cutter the closer it could be to the central shaft. The useof different sized cutters creates problems, however, because they tendto wear out at different times and it is difficult to provide a smallcutter that will withstand the high stresses encountered.

SUMMARY OF THE INVENTION The bit of this invention has a plurality ofstages with each stage having a series of cutters surrounding a centralshaft. The consecutive stages progressively increase in diameter therebyallowing a pilot hole to be enlarged to the desired size. The stagedconfiguration provides a stabilizing efiect which reduces wandering ofthe bit as drilling proceeds and helps maintain a smooth drillingoperation.

The individual cutters are removable which allows parts to be replacedwithout replacing the entire structure. The bit of this invention allowslarge cutters to be used on the innermost stage, thus providing completeinterchangeability of cutters on the bit which results in a bit that isstronger than those of the prior art. The use of large cutters on allstages of the bit also provides simplicity and economy to the drillingoperation.

The innermost cutters are turned inwardly. This provides room for thesaddle support next to the stem and consequently a stronger bit. Thereis little, if any, need to mill or relieve into the central shaft. Inaddition, the unique inner cutters insure that there will be verylittle, if any, uncut bottom next to the pilot hole.

The cutters may be located close together which results in a bit that ismore compact than those of the prior art. The compactness providessimplicity, economy and a bit that is stronger than those of the priorart.

It is therefore an object of the present invention to provide a bit forboring large-diameter holes that is stronger and more efficient thanthose of the prior art.

It s a further object of the present invention to provide a bit fordrilling large-diameter holes that has interchangeable cutters.

It is a further object of the present invention to provide a bit fordrilling large-diameter holes that is more compact than those of theprior art.

It is a still further object of the present invention to provide greatereconomy in boring large-diameter holes.

It is a still further object of the present invention to provide a bitfor drilling large-diameter holes that eliminates the problemsassociated with having portions of uncut bottom next to the stem.

The above and other objectives and advantages will become apparent froma consideration of the following detailed description when taken inconjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows a bit of the prior art.

FIG. 2 is an enlarged view of one of the small inner cutters of theprior art bit shown in FIG. 1.

FIG. 3 shows one embodiment of the present invention.

FIG. 4 is a top view of the bit shown in FIG. 3.

FIG. 5 is an enlarged view of one of the inner cutters of the bit of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG. 1, a bit ofthe prior art is shown generally at 10. Two small inner cutters 11 and12 are positioned next to the central shaft 13 and function as the firstcutting stage. At least two cutters are used to insure a valanceddrilling bit and a smooth drilling operation. Cuters 11 and 12 are heldin position by saddles 14 and 15 vhich are mounted on central shaft 13.The saddles 14 and .5 allow the cutters to be easily removed and newcutters nserted. An example of a removable cutter and saddle sysem isshown in US. Pat. No. 3,203,492 to C. L. Lichte, ratented Aug. 31, 1965.A second cutting stage is located )elow the first stage and includes twolarge cutters 16 and .7 mounted in saddles 18 and 19.

The central shaft 13 extends through a pilot hole having a liameterslightly larger than the diameter of shaft 13. The it 10 is rotated bymeans of a system well known in the LI'I. As bit 10 rotates the cutters11, 12, 16 and 17 contact .nd disintegrate the formation as the bit ismoved along the rilot hole. The cutting surfaces of cutters 11, 12, 16and 17 must traverse the entire surface of the hole being bored and hesaddles and other portions of the bits must not contact he formationsbeing drilled. In order to accomplish this he inside cutting edges 20and 21 of cutters 11 and 12 must to as close to central shaft 13 aspossible and cutters 16 Llld 17 of the second cutting stage must bepositioned with heir inside cutting edges below the outside cuttingedges of utters 11 and 12. Consequently the inside cutters 11 and .2 arelimited in size and the central shaft must have a ecess to accommodatesaddles 14 and 15.

Referring now to FIG. 2, one of the inner cutters of the irst stage isshown in greater detail. To insure that saddle .4 does not contact theformation being drilled, the axis 22 If cutter 11 is at an angle to axis23 of the central shaft .3. The angle 0 must be greater than 90 and isgenerally [1 the range of 120 to 130. The central shaft 13 must inlude arecess 24 to accommodate saddle 14 and cutter 11. The recess 24 weakensthe central shaft 13 and is therefore Lndesirab-le.

Referring now to FIG. 3, one embodiment of the present uvention is showngenerally at 25. One pair of inner cuters 26 and 27 are positioned nextto the central shaft 28. This pair of cutters 26 and 27 is turned inwardin a manner hat will be explained more fully with regard to FIG. 5. Aecond pair of cutters 29 and 30 are included in the first tage. Cutters29 and 30 are turned outward in the convenional manner but are set outfrom the central shaft 28 suflicient distance to accommodate the saddlesof cutters .9 and 30 without requiring a recess in the central shaft 28.lutters 31, 32, 33 and 34 make up the second stage in a manner similarto that described in connection with IG. 1.

A top view of bit 25 is shown in FIG. 4. Inner cutters 26 ,nd 27 arepositioned on opposite sides of central shaft 28 nd turned inward. Theother pair of inner cutters 29 and 0 of the first stage are set out fromcentral shaft 28 and urned outward. The second stage including cutters31, 32, '3, and 34 is located below the other cutters and spaced toirovide a balanced bit. It can be appreciated that as the bit srotatedthe cutters will contact all portions of the formaion to insure auniform drilling operation.

One of the inner cutters 26 is shown in greater detail in "16. 5. Theaxis 35 of cutter 26 is at an angle to the axis 6 of shaft 28. The angleis less than 90 and in this emodiment is an angle of 57. It is beunderstood that odiment is an angle of 57. It is to be understood thatnay be an angle other than 57 and in general is within he range of from45 to 90. The cutter 26 is the same size arge cutter used at otherlocations on the bit 25. This inorporates all of the advantages of usinglarge cutters inluding complete interchangeability, greater strength,conomy and a larger cutting area. The inner edge 37 of utter 26 islocated close to central shaft 28 insuring that here will be verylittle, if any, uncut bottom next to he central shaft. In circumstanceswherein a small amount f uncut bottom re'mains between point 37 and stem36, he formation will break away much easier than when usng bits of theprior art. Any uncut bottom with bits of the rior art such as the bitshown in FIG. 1 will be larger than 'with a bit of this invention. Inaddition, the uncut bottom will have greater support from the formationabove because the cutter is at an obtuse angle. The saddle 38 supportingcutter 26 is positioned next to central shaft 28 without a large recessto accommodate it. This results in a stem that is stronger than those ofthe prior art and in general a bit that is stronger, more efiicient andcompact than those of the prior art.

Referring again to FIG. 3, the operation of bit 25 will be described.The bit 25 is rotated and moved along a pilot hole according to a systemwell known in the art. The first pair of inner cutters 26 and 27 contactthe formations nearest the central shaft and disintegrate them as thebit is moved along the pilot hole. It is to be understood that anynumber of cutters may be used to carry out this operation. The bitshould be balanced so as to insure a smooth boring operation and inorder to balance the bit a plurality of cutters should be used, spacedat regular intervals around the central shaft. The second pair of innercutters 29 and 30 contact the formations at a point spaced from thecentral axis. Cutters 29 and 30 may be slanted outward in theconventional manner described in connection with FIG. 1. The cutters 29and 30 disintegrate the formations as the bit is moved along the pilothole and protect the saddles supporting cutters 26 and 27. In order tomaintain a balanced bit it is to be understood that a plurality ofcutters spaced at regular intervals may be utilized as previouslydiscussed. The second stage of cutters, including cutters 31, 32, 33 and34, trail the first stage and enlarge the hole to the desired size. Itis to be understood that more than two stages may be provided if a stilllarger hole is desired and that two stages are shown for illustrationpurposes.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A bit for enlarging a pilot hole into a large-diameter holecomprising:

a central shaft having a central longitudinal axis;

a main bit body attached to said central shaft, said main bit bodyincluding a plurality of drilling stages progressively increasing insize;

the first of said drilling stages including a pair of rolling cutters,removably mounted in a corresponding pair of saddles, the axis ofrotation of said rolling cutters turned inward at an acute angle to thecentral longitudinal axis of said shaft; and

a second pair of rolling cutters, removably mounted in a correspondingsecond pair of saddles, the axis of rotation of said second pair ofrolling cutters turned outward at an obtuse angle to the centrallongitudinal axis of said shaft.

2. The bit of claim 1 wherein the second of said drilling stagesincludes a plurality of rolling cutters removably mounted in acorresponding plurality of saddles, the axis of rotation of said rollingcutters turned outward at an obtuse angle.

3. The bit of claim 2 wherein all of said rolling cutters are the samesize.

4. The bit of claim 3 wherein said acute angle is within the range offrom 45 to 5. A bit for enlarging a small-diameter pilot hole into alarge-diameter hole comprising:

a central shaft having a central longitudinal axis, said central shafthaving an upper end adapted to fit within the pilot hole;

a main bit body attached to said central shaft, said main bit bodyhaving a diameter larger than the diameter of the pilot hole;

a plurality of drilling stages positioned on the main bit body, saiddrilling stages progressively increasing in size;

the first of said drilling stages including a pair of rolling cutters,removably mounted in a corresponding pair of saddles, the axis ofrotation of said rolling cutters turned inward at an acute angle to thecentral axis of said shaft; and

the [record] second of said drilling stages including a plurality ofrolling cutters removably mounted in a corresponding plurality ofsaddles, the axes of rotation of said plurality of rolling cuttersturned outward at an obtuse angle.

6. The bit of claim wherein all cutters are the same size.

7. The bit of claim 5 wherein said acute angle is within the range offrom 45 to 90.

8. The bit of claim 5 wherein said acute angle is approximately 57.

9. A bit for enlarging a pilot hole into a large-diameter hole bydisintegrating the formations surrounding the pilot hole, comprising:

a bit body;

a central shaft projecting from said bit body;

first rolling cutter means connected to said bit body for contacting anddisintegrating formations surrounding the pilot hole, said first rollingcutter means having first cutting surface means for contactingformations surrounding the pilot hole with said first cutting surfacemeans being turned inward toward said central shaft; and

second rolling cutter means connected to said bit body for contactingand disintegrating formations surrounding the pilot hole, said secondrolling cutter means having second cutting surface means for contactingformations surrounding the pilot hole with said second cutting surfacemeans being turned outward away from said central shaft.

10. The bit of claim 9 wherein said first rolling cutter means includesa first pair of rolling cutters, removably mounted in a correspondingpair of saddles with said first pair of rolling cutters having firstcutting surfaces that are turned inward toward said central shaft; andwherein said second rolling cutter means includes a plurality of secondrolling cutters, removably mounted in a corresponding pair of saddleswith said second rolling cutters having second cutting surfaces that areturned outward away from said central shaft.

11. A bit for enlarging a small diameter pilot hole into a largediameter hole by disintegrating the formations surrounding the pilothole and insuring that there will be very little, if any, uncut bottomnext to the pilot hole, comprising:

a central shaft with a central longitudinal axis, said central shafthaving an upper portion with a diameter small enough to fit within saidpilot hole;

a bit body projecting from said central shaft, said bit body having adiameter larger than the diameter of the upper portion of the centralshaft and larger than the diameter of the pilot hole;

at least one first rolling cutter positioned on said bit body proximatesaid central shaft, said first rolling cutter having an axis ofrotation, with the angle between said central longitudinal axis and saidaxis of rotation measured from said upper portion of said central shaftbeing within the range of from approximately 45 to approximately and atleast one second rolling cutter positioned on said bit,

said second rolling cutter having an axis of rotation, with the anglebetween the central longitudinal axis and said axis of rotation measuredfrom said upper portion of said central shaft being greater thanapproximately 90.

12. The bit of claim 11 wherein said first rolling cutter includes afirst cutting surface for contacting formations surrounding the pilothole with said first cutting surface being turned inward toward saidcentral shaft; and wherein said second rolling cutter includes a secondcutting surface for contacting formations surrounding the pilot holewith said second cutting surface being turned outward away from saidcentral shaft.

References Cited The following references, cited by the Examiner, are ofrecord in the patented file of this patent or the original patent.

UNITED STATES PATENTS 839,837 1/ 1907 Guttzeit 355 X 1,747,908 2/ 1930Seifert 175-334 2,208,530 7/1940 Thompson 175-335 2,703,698 3/1955Westerman 175-334 2,868,510 1/1959 Dean 175-344 X 2,949,281 8/1960 Bauret a1 175-356 X 1,826,059 10/1931 Dunn et a1. 174334 3,285,355 11/1966Neilson et a1. 175-334 1,322,696 11/1919 Hughes 175353 2,064,273 12/1936Scott 174-342 X 2,122,808 7/1938 Catland 174357 X 3,437,380 4/1969Lawrence 175-62 X FOREIGN PATENTS 1,257,200 2/1961 France 175-3341,297,278 5/1962 France 17553 DAVID H. BROWN, Primary Examiner U.S. Cl.X.R. 17553, 344

